Prioritize longer keywords also when they're not alphanumeric

Author: ltrzesniewski

.gitignore

@@ -45,6 +45,9 @@ bld/
 # Visual Studio 2017 auto generated files
 Generated\ Files/
 
+# JetBrains Rider
+.idea/
+
 # MSTest test Results
 [Tt]est[Rr]esult*/
 [Bb]uild[Ll]og.*

ICSharpCode.AvalonEdit.Tests/Highlighting/XmlHighlightingDefinitionTests.cs

@@ -0,0 +1,39 @@
+using System.Linq;
+
+using ICSharpCode.AvalonEdit.Document;
+using ICSharpCode.AvalonEdit.Highlighting;
+using ICSharpCode.AvalonEdit.Highlighting.Xshd;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.AvalonEdit.Tests.Highlighting
+{
+	[TestFixture]
+	public class XmlHighlightingDefinitionTests
+	{
+		[Test]
+		public void LongerKeywordsArePreferred()
+		{
+			var color = new XshdColor { Name = "Result" };
+			var syntaxDefinition = new XshdSyntaxDefinition {
+				Elements = {
+					color,
+					new XshdRuleSet {
+						Elements = { new XshdKeywords {
+								ColorReference = new XshdReference<XshdColor>(null, color.Name),
+								Words = { "foo", "foo.bar." }
+							}
+						}
+					}
+				}
+			};
+
+			var document = new TextDocument("This is a foo.bar. keyword");
+			var highlighter = new DocumentHighlighter(document, new XmlHighlightingDefinition(syntaxDefinition, HighlightingManager.Instance));
+			var result = highlighter.HighlightLine(1);
+
+			var highlightedText = document.GetText(result.Sections.Single());
+			Assert.That(highlightedText, Is.EqualTo("foo.bar."));
+		}
+	}
+}

ICSharpCode.AvalonEdit/Highlighting/Xshd/XmlHighlightingDefinition.cs

@@ -240,9 +240,9 @@ public object VisitKeywords(XshdKeywords keywords)
 					}
 					keyWordRegex.Append(@")\b");
 				} else {
-					keyWordRegex.Append('(');
+					keyWordRegex.Append("(?>");
 					int i = 0;
-					foreach (string keyword in keywords.Words) {
+					foreach (string keyword in keywords.Words.OrderByDescending(w => w.Length)) {
 						if (i++ > 0)
 							keyWordRegex.Append('|');
 						if (char.IsLetterOrDigit(keyword[0]))